The remains handed over by North Korea last week in 55 boxes are “consistent with being Americans” based on an initial examination, according to a US scientist.
The expert, who has seen the remains, said none have been positively identified.
Although President Donald Trump has publicly thanked North Korean leader Kim Jong Un for fulfilling the promise he made at their June 12 Singapore summit to return American war remains, US officials cautioned that little was known about the remains and that they could not be quickly identified.
John E. Byrd, director of the Defence Department laboratory in Hawaii where the 55 cases arrived on Wednesday, cited several reasons for saying at least some of the remains appear to be those of Americans missing from the Korean War.
Mr Byrd was present when North Korean officials turned over the 55 boxes at Wonsan airport in North Korea last Friday, and he was among the US government specialists who made a further preliminary examination of the contents after the boxes were flown to Osan air base in South Korea the same day.
A cursory examination at Wonsan confirmed the remains were human, he said, and a closer look at Osan gave reason to believe they likely are Americans.
Mr Byrd, speaking by video teleconference from Hawaii, said: “What we saw were remains that were consistent with what we have found from the Korean War recoveries that we’ve done over the years, and we found remains that were consistent with being Americans.
“We have remains that look to have been in a state of preservation consistent with coming from the Korean War era,” adding that materials provided with the remains included US-issued military equipment such as canteens and buttons.
He said the remains are “good candidates to be missing Americans from the Korean War” where thousands died on battlefields and in prisoner-of-war camps during the 1950-53 conflict and remain officially unaccounted for.
Mr Byrd said he would not venture a guess at how many individuals are represented by the bones contained in the 55 boxes.
The US and North Korean militaries conducted joint excavations of war remains in the North between 1996 and 2005, yielding more than 200 set of remains – not all of which have been positively identified.
Separately, North Korea had handed over 208 boxes of remains between 1990 and 1994, some of which have also yet to be identified.
When the North Koreans turned over the 55 boxes to Byrd and other US officials at Wonsan on July 27 they said the cases contained remains of an undetermined number of Americans, but the only identification item provided was a single military dog tag, Mr Byrd said.
Two members of that person’s family have been notified, Kelly McKeague, the director of the Defence POW-MIA Accounting Agency, told reporters.
Mr McKeague declined to reveal the name on the dog tag.
Mr Byrd said the North Koreans at Wonsan provided what he described as a “short bit, a little paragraph of information” with each of the 55 boxes.
The most significant bit of information in each case was the name of the village where the remains were recovered, he said.
One of the villages was Sin Hung-ri, which he said is on the east side of the Chosin Reservoir where US Army soldiers fought a fierce battle in the fall of 1950 after Chinese forces entered the war.
North Korea had told American officials more than once in recent years that it had about 200 sets of US war remains in storage.
Mr McKeague said the North Koreans who provided the 55 boxes last week did not say whether they have others.
He added the US is prepared to discuss arrangements for future US-North Korean excavations but this process is not yet underway, but his laboratory in Hawaii has already begun working on the remains.
The first step, he said, is sampling the bones for DNA that potentially could be matched with DNA samples provided over the years by relatives of Korean War MIAs.
If matches are achieved, identification can be done relatively quickly, he said, but in other cases the identification work will take years.
The forensics work in some cases is aided by records of chest X-rays that US soldiers commonly were given upon entering the military, as well as dental records.